There has been an increasing demand for remotely controllable circuit breaker assemblies that can reciprocate between an open circuit and a closed circuit in response to a remotely generated command. One advantageous application for such circuit breaker assemblies is in control panelboards that are used for automated control systems such as building management systems. Building management systems may include automated lighting systems, HVAC control systems, fire control, security, and control of refrigerator/freezer systems. Automated lighting systems have been developed for the control of lighting circuits based upon inputs such as the time-of-day, wall switches, occupancy sensors and/or control from a power distribution system. Lighting control systems offer an opportunity to save energy by automating the process of cutting back on the number of lighting fixtures that are illuminated, automatically turning off lighting fixtures when they are not required, or by cutting out artificial lighting altogether when circumstances warrant. For example, ambient light sensors can be used to control lighting circuits in response to ambient light levels. The sensors can serve both switching and automatic dimming functions that can adjust the output of the lighting system continually in response to the amount of daylight striking the ambient light sensor. Occupancy sensors can be used to activate lighting when someone is in a space and to deactivate the lighting, perhaps after a set time interval, when a person is no longer detected in the space.
In general, circuit breaker assemblies that can be remotely controlled may be divided into at least two classes. The first is the remote-operated circuit breaker. In a remote-operated circuit breaker, two pairs of contacts are located within a single package. The first (or primary) pair of contacts is used to interrupt short circuits, to interrupt overloads, and to switch the circuit breaker on and off via a handle. The second pair of contacts in a remote operated circuit breaker may be used, for example, in a lighting control application. In some applications, a single pair of contacts serves both functions.
Another class of remotely controlled circuit breaker assemblies is an assembly that includes a circuit control pod, or lighting control pod. In such an assembly, a separate relay device or “pod,” including a mechanism to operate a pair of contacts remotely, is attached to a standard circuit breaker that does not have a means of remote operation. The circuit control pod adds an additional pair of contacts in series with the circuit breaker.
Several types of mechanisms have been used to remotely operate the contact pair in a circuit control pod. Those include a bi-directional solenoid with an over-center spring, a worm-gear actuated DC motor system, and a multi-linkage solenoid driven mechanism.
In the over center design, a solenoid must be sized to work against a non-linear spring force. The solenoid must furthermore have two coils to operate bi-directionally. Those factors can increase the size of the required mechanism.
The worm-gear motor design produces a loud noise due to the operation of the DC motor. The worm-gear design is furthermore prone to slippage and failure of the mechanism. Also, when applied in arrays such as those found in standard panel boards having 42 devices, issues such as motor in-rush and under-voltage conditions in the power line must be overcome by increasing the size and complexity of power supplies or the power management system.
The multi-linkage solenoid driven mechanism has the disadvantage of requiring several points of rotation, and numerous moving parts. In typical applications, multiple springs are required. Given that a lighting control device is expected to cycle 50,000-100,000 times during its life, the use of multi-spring assemblies increases the risk that frictional wear will cause the mechanism to fail during its intended life.
U.S. Pat. No. 4,816,792 to Belbel et al. describes a main circuit breaker contact that may be remotely operated by an electromagnet. The design incorporates a permanent magnet for holding an armature in position. The permanent magnet mechanism operates directly on the circuit breaker contacts. Such a design increases the mass of the circuit breaker mechanism and thus results in parasitic loading of the breaker mechanism, degrading performance.
U.S. Pat. No. 6,531,938 to Smith et al. teaches a remote operated circuit breaker assembly having a remote module for remotely operating the circuit breaker. A motor disposed in the module housing operates the breaker switch remotely. The mechanism requires actual operation of the handle of the breaker. Because the breaker handle requires greater force, the actuating device must be a larger and higher-cost unit.
There is presently a need for an improved design and method for opening and closing remote controlled contacts. Such a design should have a low cost and should be of high reliability. Such a design should furthermore be compact for use in a small package area. To the inventors' knowledge, no such design is currently available.